1. Field of the Invention
The present invention relates to an excess air factor control device for an alcohol reformed gas engine for use in transportation vehicles, power generation and rotary machines.
2. Description of the Prior Art
Such an alcohol reformed gas engine using a gas fuel mainly containing hydrogen and carbon monoxide obtained by reforming alcohol is superior particularly for use in an automobile because of its high thermal efficiency and relatively clean exhaust gas. The engine, however, has the following three disadvantages.
(1) At an excess air factor (less than 1.3) near a stoichiometrical air fuel ratio, there is a tendency of the engine to cause extraordinary burning such as backfiring and therefore combustion control is difficult, so that the maximum torque is suppressed to a lower value.
(2) In order to operate the engine with reformed gas over all the operation modes, a reforming device becomes unavoidably large and highly expensive.
(3) In warm-up or idling operation for long periods of time (e.g. more than twenty minutes), the temperature of the reforming device becomes low to an extent such that the reformed gas is not produced and therefore to stop the supply of the gas required for engine operation.
To solve these problems, it has been suggested to temporarily supply alcohol as it is to an engine. In other words, the engine is operated only with the reformed gas during normal operating condition such as acceleration and deceleration in streets or cruise travelling at speeds lower than 100 km/hour and alcohol is supplied to the engine when the supply of the reformed gas is stopped under a condition of the maximum torque seldom used, a high speed more than 100 km/hour, warm-up, idling for a long period of time or the like. Such a suggestion was, however, only an idea without any concrete controlling method and device, because of a difficulty to realize it.